style part

.aa{position:absolute;transition:top 2s;}

html part

<div id="ele" class="aa"></div>

js part

var ele=document.getElementById("ele")
ele.onclick=function(){
    ele.style.top=0
//ele.style.top=100+"px"setTimeouttop0100
setTimeout(function(){
    ele.style.top=100+"px"
},0)
}

online preview address
http://jsbin.com/pucedelowa/e.

now there is a doubt, why only put ele.style.top=100+"px" in seTimeout, click on the text will have the animation effect of transition?
are there any other functions that can achieve the same effect as setTimeout?